Automatic transmission with hydraulic operator having nested drums

ABSTRACT

A compact clutch device in an automatic transmission, wherein an input shaft (15) is provided thereon with a first drum (111) rotatably and axially slidably connected to the input shaft (15) through the inner peripheral portion of a rotatably supporting portion (112). A second drum (117) has, at its inner peripheral portion of, a rotatably supporting portion (120) of which is relatively rotatably coupled onto the outer peripheral portion of the rotatably supporting portion (112) of the first drum (111). The inner side of an outer cylinder of the first drum (111) and a hub portion (119) provided on the radial surface of the second drum (117) are engageably interconnected through a first clutch (C1). The inner side of an outer cylinder of the second drum (117) and a rotatable element (R2) of a planetary gear unit (12) are engagebly interconnected through a second clutch (C0), and the second drum (117) is also selectively connected to another rotatable element (R1) of the planetary gear unit (12 ) through a clutch.

TECHNOLOGICAL FIELD

The present invention relates to a compact clutch system for anautomatic transmission.

TECHNOLOGICAL BACKGROUND

Generally speaking, automatic transmission of the so-called "Simpsontype" has two single planetary gear units which share sun gears and inwhich the carrier of the first planetary gear unit and the ring gear ofthe second planetary gear unit are integrally connected to each other.Thus, the forward 3rd speed is established by selectively inputting tothe ring gear or sun gear of the first planetary gear unit through aclutch, by stopping certain rotary components of the planetary gearunits by brakes or one-way clutches, and by outputting from the ringgear of the second planetary gear unit connected integrally to thecarrier of the first planetary gear unit.

A four-speed prior art automatic transmission is based upon theaforementioned three-speed automatic transmission mechanism composed ofthe two planetary gear units and establishes a forward 4th gear stage byaddition of an over-drive (O/D) mechanism or an underdrive (U/D)mechanism composed of a single planetary gear unit.

In the automatic transmission having the O/D mechanism, moreover, theoutput member, i.e., the ring gear of this O/D mechanism, is axiallyconnected to the input member of the three-speed automatic transmissionmechanism.

In the automatic transmission shown in FIG. 6, for example, an O/Dmechanism is attached to a three-speed automatic transmission mechanism10₁ (as shown at a lower half with respect to line L of FIG. 6) toprovide a four-speed automatic transmission mechanism (as shown at anupper half from the line L of FIG. 6). This example is equipped with anO/D mechanism clutch C0, through which rotation of the input shaft istransmitted to the ring gear R2 of the dual planetary gear units.

In view of recent trends toward the FF type automobile and a higheroutput power, the automatic transmission is desired to have a smallersize and a larger capacity of transmission torque. However, theseobjectives cannot be satisfied by the aforementioned four-speedautomatic transmission which is composed of the three planetary gear,including an O/D mechanism or the like, as has been described inconnection with the prior art.

Specifically, in the example shown in FIG. 6, the O/D mechanism (i.e.,including the clutch C0) is attached to the input shaft of thethree-speed transmission mechanism so that the axial size of theautomatic transmission is increased. Since, moreover, the ring gear R2or the input member of the O/D mechanism is connected by an extensionradially outward of the clutch C1, the radial size of the automatictransmission is also increased.

According to the simplest structure, moreover, the r.p.m. sensor of theinput shaft is attached to the transmission casing 17a to measure ther.p.m. of the drum 130 of the clutch C0. With this structure, however,the r.p.m. of the input shaft cannot be measured from the clutch C0 drum130 which is not rotated at all times.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a clutch system for anautomatic transmission, which can achieve the four-speed transmissionmechanism without any increase in the axial and radial sizes, ascompared with the three-speed transmission mechanism.

Another object of the present invention is to provide a clutch systemfor a four-speed automatic transmission mechanism which allowsattachment of an input r.p.m. sensor without any difficulty.

In order to achieve the above-specified objects, according to thepresent invention, there is provided a clutch system for an automatictransmission comprising an automatic transmission mechanism including: aplanetary gear unit 12; an input shaft 15 connected to a plurality ofrotary components of said gear unit 12 through individual clutches; anoutput member connected to a predetermined one of the rotary componentsof said gear unit; and stop means for stopping a predetermined one ofthe rotary components of said gear unit 12, which system comprises: afirst drum 111 axially slidably mounted on said input shaft 15 throughrotatably supporting portion 112 and is secured against rotationrelative to shaft 15; and a second drum 117 having its rotatablysupported by supporting portion 120 having its inner surface in contactwith the outer circumference of the rotatably supporting portion 112 ofsaid first drum 111, wherein the inner surface of the outer flangeportion of said first drum 111 and a hub portion 119 formed on theradial flange portion of said second drum 117 are freely engaged with orreleased from each other through a first clutch C1, wherein said seconddrum 117 has its outer flange portion its inner surface freely engagedwith or released from one rotary element R2 of the planetary gear unit12 through a second clutch C0, and wherein said second drum 117 isfreely engaged with or released from another rotary element R1 of saidplanetary gear unit 12.

According to the present invention, the clutch system comprises: a firstdrum 111 mounted against rotation and axially slidable on input shaft 15through a rotatably supporting portion 112; and a second drum 117 havingits rotatably supporting portion 120 having its inner surface rotatablymounted on the outer circumference of the rotatably supporting portionof the first drum 111, wherein the inner surface of the outercylindrical portion of the first drum 111 and a hub portion 119 formedon the radial flange portion of the second drum 117 are freely engagedwith or released from each other through a first clutch C1, and whereinthe inner surface of the outer cylindrical portion of the second drum117 and the ring gear R2 of the planetary gear unit are freely engagedwith or released from each other through the second clutch C0. As aresult, the rotation of the input shaft of the automatic transmission istransmitted to the ring gear R2 of the planetary gear unit by theengagements of the first clutch C1 and the second clutch C0 so that thetarget gear stage, e.g., the 4th speed gear stage is achieved throughthe planetary gear unit.

As a result, the second drum 117 encircling the second clutch C0 forestablishing the 4th speed is supported on the supporting portion 112 ofthe first drum 111 so that the axial size of the clutch system of thepresent invention can be accordingly reduced. Specifically, therotatably supporting portion (or axially supporting portion) 120 of thesecond drum 117 is positioned radially outward of the rotatablysupporting portion (or splined portion) 112 of the first drum 111 sothat the axial distance can be shortened by the length of the rotatablysupporting portion 120 of the drum 117 (i.e., the length correspondingto the bearing 131 of the C0 drum 130, as shown in FIG. 6).

Moreover, the second drum 117 can be engaged with the ring gear R2 ofthe planetary gear unit without an axial extension radially outward ofthe external diameter of the first drum 111 so that the radial size isnot increased.

Since, furthermore, the second drum 117 is arranged between the torqueconverter 50 and the first drum 111, drum 111 can be located near theouter casing 17 of the transmission so that the sensor for detecting ther.p.m. of the input shaft can be attached in the vicinity of the firstdrum 111.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a section showing a clutch system of the present invention.

FIG. 2 is a section of an automatic transmission to which the presentinvention is applied.

FIG. 3 is a schematic diagram showing the automatic transmission of FIG.2.

FIGS. 4-a and 4-b are circuit diagrams showing the whole structure of ahydraulic control system.

FIG. 5 is a table enumerating the operations of a shift gear mechanism.

FIG. 6 is a section showing the four-speed automatic transmission of theprior art.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail in the following inconnection with the embodiment thereof with reference to theaccompanying drawings.

FIG. 3 is a schematic diagram showing the automatic transmission, andFIG. 2 is a section showing the automatic transmission to which thepresent invention is applied.

A four-speed automatic transmission according to the present inventionis constructed of a torque converter 50 having a lockup clutch L/C, afour-speed shift gear mechanism 1, a reduction mechanism 51 and adifferential mechanism 52.

The four-speed shift gear mechanism 1 is equipped with a planetary gearunit 12 which is a combination of a single planetary gear 10 and a dualplanetary gear 11. This gear unit 12 has its sun gears S1 and S2integrated into a sun gear S. Moreover, pinions P1 and P1' meshing withthe sun gears S1 and S2 share a carrier CR. This carrier CR is sharedwith that CR supporting said pinions and a pinion P2 meshing with a ringgear (referred hereinafter to as the "large ring gear") R2 of the dualplanetary gear 11.

Moreover, an input shaft 15 extending from the output member of thetorque converter 50 is connected through a first clutch C1 to aconnecting member 16 and through a second clutch C2 to the sun gear S.Between the connecting member 16 and the ring gear (referred tohereinafter as the "small ring gear") R1 of the single planetary gear10, there are interposed the third clutch C3 and a second one-way clutchF0. A fourth clutch C0 is interposed between the connecting member 16and the large ring gear R2.

On the other hand, the aforementioned sun gear S can be stopped by afirst brake B1 which is a band brake. Between the large ring gear R2 anda casing 17, there are interposed a second brake B2 and a first one-wayclutch F1. Moreover, the carrier CR is connected to an output gear 13which is positioned generally at the center of the shift gear mechanism1.

The reduction mechanism 51 is equipped with a counter shaft 54 which isrotatably supported by the casing 17. On the counter shaft 54, there arefixed a large gear 53 meshing with the aforementioned output gear 13 atall times, and a small gear 55.

The differential mechanism 52 is composed of a differential pinion 56and lefthand and righthand pinions 57a and 57b meshing with each other.These pinions 57a and 57b are fixed on lefthand and righthand frontaxles 59a and 59b, respectively. The differential pinion 56 is supportedby a differential carrier 60 which in turn is rotatably supported by thecasing 17. On the differential carrier 60, there is fixed a ring gear 61which meshes with the aforementioned small gear 55 at all times.

FIGS. 4-a and 4-b are diagrams showing the hydraulic control system ofthe automatic transmission of the present invention. In these Figures, ahydraulic control system U is equipped with hydraulic servos C₁, C₂, C₃and C₀, and B₁ and B₂ for actuating the clutches C1, C2, C3 and C0 andthe brakes B1 and B2, respectively. Of these, the first clutch hydraulicservo C₁, the second clutch hydraulic servo C₂, the fourth clutchhydraulic servo C₀, and the first brake hydraulic servo B₁ arerespectively arranged with accumulators 2₁, 2₂, 2₃ and 2₄ in paralleltherewith.

Numeral 62 designates a manual valve which has its oil passages switchedby the shifting operations of the driver to individual ranges. Themanual valve 62 has: its D port communicating with a line pressurepassage PL in the D range; its D and 2nd ports in the 2nd range; its D,2nd and 1st ports in the 1st range; and its R port in the R range.

Numeral 3 designates a primary regulator valve which is actuated by athrottle pressure or the oil pressure coming from the R range port toregulate the oil pressure coming from a pump 63, to generate the linepressure. Numeral 5 designates a throttle pressure control valve whichis controlled by an electric signal based upon the throttle opening togenerate a predetermined throttle pressure (Pth).

Said throttle pressure control valve 5 is equipped with a solenoid 5a,which is controlled by the electric signal coming from a not-showncontrol unit, and an input port 5b and an output port 5c. The throttlepressure Pth coming from the output port 5c is fed to a throttlepressure port 3a of the primary regulator valve 3 and to a feedback port20c of an accumulator control valve 20.

65 Designates a solenoid modulator valve for modulating the linepressure, to the input port 5b of the throttle pressure control valve 5.The accumulator control valve 20 is equipped with not only an input port20a but also a control port 20b and the feedback port 20c. The oilpressure at the control port 20b is fed to the back pressure chambers 7₁to 7₄ of the aforementioned accumulators 2₁ to 2₄.

Moreover, these accumulators 2₁ to 2₄ are equipped with pistons 6₁ to 6₄which have their front faces defining accumulator chambers 9₁ to 9₄communicating with the individual hydraulic servos and have their backfaces defining the back pressure chambers 7₁ to 7₄ having pressurereceiving areas equal to those of the accumulator chambers. At the frontfaces of said pistons 6₁ to 6₄, there are disposed a shorter spring 66and a longer spring 67, as exemplified in the accumulator 2₁.

Moreover, all of these accumulators are made to have an identical shapeand to share common parts.

The third clutch hydraulic servo C₃ is equipped with a modulator valve68, but the second brake hydraulic servo B₂ is fed either directly withthe line pressure or indirectly with the modulator pressure through themodulator valve. Thus, both of these hydraulic servos C₃ and B₂ notequipped with an accumulator.

There are also provided a 1-2 shift valve 36, a 2-3 shift valve 37 and3-4 shift valve 39, of which: the 1-2 shift valve 36 and the 3-4 shiftvalve 39 are controlled by a second solenoid valve S_(L) 2; and the 2-3shift valve 37 is controlled by a first solenoid valve S_(L) 1.

Specifically, the 1-2 shift valve 36 is formed with: a control oilchamber 36d exposed to the control oil pressure coming from the solenoidvalve S_(L) 2; a line pressure supply port 36a communicating the with Drange port; an output port 36b; a drain port 36c; a B₂ port 36e; a lowmodulator port 36f; and a constraining control oil chamber 36g. The 1-2shift valve 36a is held in its lower half position at the 2nd, 3rd and4th speeds and is switched to its upper half position at the 1st speed.On the other hand, the 2-3 shift valve 37 is formed with: a control oilchamber 37d exposed to the control oil pressure coming from the solenoidvalve S_(L) 1; an input port communicating with an oil line a leadingfrom the output port of the aforementioned 1-2 shift valve 36; an outputport 37b communicating with the fourth clutch hydraulic servo C₀ via anoil line b; a drain port 37c; a 1st range constraining control oilchamber 37e; a D range line pressure supply port 37f; a port 37hcommunicating with the constraining control oil chamber 36g of theaforementioned 1-2 shift valve 36; a port 37i; and a drain port 37j. The2-3 shift valve is held in its lower half position at the 1st and 2ndspeeds and is switched to its upper half position at the 3rd and 4thspeeds.

On the other hand, the 3-4 shift valve 39 is formed with: a control oilchamber 39f exposed to the control oil pressure coming from the solenoidvalve S_(L) 2; a C₀ port 39a; a B₁ release port 39b; a drain port 39e; aconstraining control oil chamber 39g communicating with theaforementioned port 37i; a 2nd range constraining control oil chamber39h; a C₃ port 39i; and a drain port 39j. The 3-4 shift valve 39 is heldin its lower half position at the 1st, 2nd and 3rd speeds and isswitched to its upper half position at the 4th speed.

Numeral 30 designates a B₁ modulator valve, which is formed with: a linepressure supply port 30b communicating with the oil line a leading fromthe output port 36b of the aforementioned 1-2 shift valve 36; a pressuremodulation port 30a; a feedback port 30d; a constraining control oilchamber 30c; and a control oil chamber 30e communicating with thepressure control port 20b of the accumulator control valve 20. The B₁modulator valve 30 reduces the line pressure coming from the linepressure supply port 30b at a predetermined ratio and outputs it to thepressure modulation port 30a, when no constraining control oil pressureis exerted upon the control oil.

Numeral 32 designates a B₁ modulator control valve which is formed with:a first input port 32d communicating with an oil line g leading from theport 37i of the aforementioned 2-3 shift valve 37; a second input port32a communicating with an oil line h leading from the port 39c of theaforementioned 3-4 shift valve 39; and an output port 32b communicatingwith the constraining control oil chamber 30c of the modulator valve 30.The B₁ modulator control valve 32 has its first input port 32d andoutput port 32b communicating with each other, when a control oilchamber 32c communicating with the hydraulic servo C₀ via an oil line cis relieved, and its second input port 32a and output port 32bcommunicating with each other when said control oil chamber 32c is fedwith the oil pressure.

A 2-3 timing valve 33, which branches the oil line b providing thecommunication between the output port 37b of the 2-3 shift valve 37 andthe fourth clutch hydraulic servo C₀, is formed with: an input port 33acommunicating with the output port 37b; an output port 33b communicatingwith the port 39a of the 3-4 shift valve 39; a first control oil chamber33d communicating with the hydraulic servo C₀ ; and a second control oilchamber 33c communicating with the pressure control port 20b of theaccumulator control valve 20. When the oil pressure of the hydraulicservo C₀ rises to a predetermined level, the 2-3 timing valve 33 has itsinput port 33a and output port 33b communicating with each other.

In an oil line d providing the communication between the hydraulic servoC₀ and the port 39a, there is disposed a check value 40 for admittingthe flow from the hydraulic servo C₀ to the port 39a. In an oil line eleading from said oil line d to the aforementioned oil line b, there isdisposed a check value 41 for allowing the oil to be discharged from theport 39a to the port 37b.

Numeral 75 designates a lockup clutch control valve; numeral 76designates a lockup clutch modulator valve; and characters S_(L) 3designates a lockup clutch controlling solenoid valve. These valves areproperly controlled at the gear stages which are indicated at doublecircles in the operation table of FIG. 5. Moreover, numeral 77designates a second regulator valve, and numeral 80 designates a C3timing valve.

Next, the operations of the present embodiment will be described in thefollowing.

At the 1st speed in which the manual valve 62 is shifted to the D range,as shown in FIG. 5, the first solenoid valve S_(L) 1 only is ON in thedrain state, but the second solenoid valve S_(L) 2 is OFF in the supplystate.

In this state, the 1-2 shift valve 36 has its control oil chamber 36dfed with the oil pressure and is in its upper half position, and the 2-3shift valve 37 has its control oil chamber 37d relieved from the oilpressure and is in its lower half position. Moreover, the 3-4 shiftvalve 39 has its control oil chamber 39f fed with the oil pressure butis constrained in its lower half position because its constrainingcontrol oil chamber 39g is fed with the line pressure from the linepressure supply port 37f of the 2-3 shift valve 37.

As a result, the first clutch hydraulic servo C₁ only is fed with theline pressure from the D range port of the manual valve 62, but no otherhydraulic servo is supplied with the oil pressure. At this time, thethrottle pressure control valve 5 is suitably operated to generate thepredetermined throttle pressure Pth on the basis of the signal comingfrom the control unit. Said throttle pressure Pth is applied to thesignal port 20c of the accumulator control valve 20 so that the linepressure supplied to the input port 20a is reduced to a predeterminedratio by the feedback pressure, and this reduced oil pressure is fedfrom the output port 20b to the back pressure chambers 7₁ to 7₄ of theindividual accumulators 2₁ to 2₄.

As a result, in the accumulator 2₁ communicating with the hydraulicservo C₁, the oil pressure of the back pressure chamber 7₁ is properlycontrolled in accordance with the engagement characteristics of thefirst clutch C1 by the throttle pressure control valve 5 so that saidclutch C1 is smoothly engaged. Simultaneously with this, not only theline pressure from the primary regulator valve 3 but also the pressuresin the back pressure chambers 7₂ to 7₄ of the remaining accumulators 2₂to 2₄ are controlled on the basis of the controls of the throttlepressure control valve 5, but the remaining clutches C0, C2 and C3 andthe brakes B1 and B2 are out of engagement and are not influenced in theleast.

In the 1st speed state, moreover, in which not only said first clutch C1but also the first and second one-way clutches F1 and F0 are engaged,the rotation of the input shaft 15 is transmitted to the smaller ringgear R1 through the first clutch C1 and the second one-way clutch F0.Since, in this state, the rotation of the larger ring gear R2 is blockedby the first one-way clutch F1, the carrier CR is drasticallydecelerated, while allowing the sun gear S to rotate idly, so that thedecelerated rotations are extracted from the output gear 13. Moreover,the rotation of this output gear 13 is decelerated by the reductionmechanism 51 and is transmitted to the lefthand and righthandaccelerator shafts 59a and 59b by the differential mechanism 52.

In the 2nd speed state, on the other hand, the second solenoid valveS_(L) 2 as well as the first solenoid valve S_(L) 1 is turned ON. Then,the 2-3 shift valve 37 and the 3-4 shift valve 39 are held in theirlower half positions, and the 1-2 shift valve 36 is switched to itslower half position by having its control oil chamber 36d relieved fromthe oil pressure. In this state, the line pressure of the D range portis applied to the oil line a via the line pressure supply port 36a andthe output port 36b and further to the line pressure port 30b of the B₁modulator valve 30.

On the other hand, the 2-3 shift valve 37 is in the state in which the Drange line pressure supply port 37f and the port 37i are communicatingwith each other, and the line pressure from said D range line pressuresupply port 37f is applied via the port 37i and the oil line g to thefirst input port 32d of the B₁ modulator control valve 32. In the firstand second speed states, said control valve 32 is in its upper halfposition so that the oil pressure at its input port 32d is applied viathe output port 32b to the constraining control oil chamber 30c of theB₁ modulator valve 30.

As a result, this modulator valve 30 is held at its lefthand halfposition, and the line pressure at the aforementioned line pressuresupply port 30b is outputted without any change to the pressuremodulation port 30a until it is applied by way of an oil line f to thebrake engaging oil pressure chamber 31 of the first brake hydraulicservo B₁. As a result, the first brake B1 has its band tightened byintensive force based upon the line pressure.

At the time of an upshift from the 1st to 2nd speeds, too, the throttlepressure control valve 5 is properly controlled like the aforementionedshift to the D range by the electric signal coming from the controlunit, and the line pressure is applied to the back pressure chambers 7₁to 7₄ of the accumulators 2₁ to 2₄ by said throttle pressure. As aresult, the B1 brake hydraulic servo B₁ is properly adjusted inaccordance with the engagement characteristics of said brake B1 byhaving its accumulator 2₄ controlled to a proper back pressure so thatthe first brake B1 is smoothly engaged.

In the meanwhile, the accumulators 2₁, 2₂ and 2₃ for the remainingclutches C1, C2 and C0 have their back pressures controlled. However,the second clutch C2 and the fourth clutch C0 are in their releasedstates and receive no influence. In the first clutch C1, the hydraulicservo C₁ has its oil pressure changed with the change in the linepressure based upon the throttle pressure change. However, this clutchC1 is already in the engaged static friction state, and the engaging oilpressure is at a level far higher than the torque load of the clutch, sothat the clutch C1 is not slipped.

In the 2nd speed state, moreover, in which the first brake B1 and thesecond one-way clutch F0 as well as the first clutch C1 are engaged, therotation of the input shaft 15 is transmitted though the first clutch C1and the second one-way clutch F0 to the smaller ring gear R1, and thesun gear S is stopped by the first brake B1. As a result, the rotationof said smaller ring gear R1 is extracted as the 2nd speed rotationsfrom the carrier CR while allowing the larger ring gear R2 to rotateidly. Here in this 1st to 2nd speed shift, the first one-way clutch F1overruns to prevent the shift shocks, which might otherwise be caused bythe engagement change.

In the 3rd speed state, moreover, the second solenoid valve S_(L) 2 ismaintained in its ON state, and the first solenoid valve S_(L) 1 isswitched to its OFF state.

In this state, the 1-2 shift valve 36 and the 3-4 shift valve 39 areheld in their lower half positions, and the 2-3 shift valve 37 isswitched to its upper half position by having its control oil chamber37d fed with the oil pressure. As a result, the line pressure of the oilline a, which is supplied via the 1-2 shift valve ports 36a and 36b, isintroduced via the input port 37a and the output port 37b into the oilline b so that it is supplied to the fourth clutch hydraulic servo C₀and the accumulator chamber 9₃ of the accumulator 2₃.

Moreover, the 2-3 shift valve 37 has the communication of its port 37iswitched from the D range line pressure supply port 37f to the drainport 37c so that the oil pressure to the first input port 32d of the B₁modulator control valve 32 is drained.

Moreover, the oil pressure supplied to the hydraulic servo C₀ is exertedvia the oil line c upon the constraining control oil chamber 80b of theC3 timing valve 80 to switch this valve 80 to the righthand halfposition. As a result, the line pressure from the line pressure port 39dof the 3-4 shift valve 39 is supplied via the port 39i to the input portof the C3 timing valve 80 and further via the output port and themodulator valve 68 to the third clutch hydraulic servo C₃.

When the oil pressure of the fourth clutch hydraulic servo C₀ and itsaccumulator 2₃ rises to a predetermined level, it is applied to thefirst control oil chamber 33d of the 2-3 timing valve 33 so that thisvalve 33 is switched to its upper half position. As a result, the oilpressure from the oil line b is quickly applied to the oil line d viathe line pressure supply port 33a and the output port 33b and further tothe brake releasing oil pressure chamber 35 of the first brake hydraulicservo B₁ via the ports 39a and 39b.

In this state, moreover, the oil pressure of the hydraulic servo C₀ isexerted via the oil line c upon the control chamber 32c of the B₁modulator control valve 32 to switch this valve 32 to its lefthand halfposition. However, the 3-4 shift valve 39 has its port 39c communicatingwith the drain port 39e, and the B₁ modulator control valve 32 has itssecond input port 32a as well as its first input port 32d drained. As aresult, the B₁ modulator valve 30 is in its pressure modulating state sothat its line pressure supply port 30b has its line pressure reduced ata predetermined ratio by the feedback pressure of the feedback port 30d.Thus, said modulator pressure is exerted through the oil line f upon thebrake engaging oil pressure chamber 31 of the first brake hydraulicservo B₁.

As a result, in this hydraulic servo B₁, the line pressure acting uponthe brake releasing oil pressure chamber 35 overcomes the modulatorpressure acting upon the brake engaging oil pressure chamber 31 torelease the band brake B1. At this time, the oil pressure of thehydraulic servo C₀ communicating with the accumulator 2₃ is boosted toswitch the 2-3 timing valve 33. As a result, the oil pressure isprevented from being quickly supplied to the brake releasing oilpressure chamber 35. Thus, the first brake B1 is prevented from beingreleased prior to the engagement of the fourth clutch C0, andaccordingly return for even an instant to the first speed is prevented.

At the shift from the 2nd to 3rd speed, moreover, the throttle pressurecontrol valve 5 is also properly controlled by the electric signal, andthe line pressure is controlled according to said throttle pressure bythe accumulator control valve 20. This controlled pressure is suppliedto the back pressure chambers 7₁ to 7₄ of the accumulators 2₁ to 2₄ andto the second control chamber 33d of the 2-3 timing valve 33.

As a result, the accumulator back pressure control is performed likebefore on the basis of the throttle pressure control valve 5, and theoil pressure of the hydraulic servo C₀ is controlled to match theengagement characteristics of the clutch C0 so that said clutch C0 issmoothly engaged. At the same time, the switching timing of the timingvalve 33 is properly adjusted to time the engagement of the fourthclutch C0 and the release of the first brake B1.

Simultaneously with this, the control oil chamber 30e of the B₁modulator valve 30 is also supplied with the oil pressure from theoutput port 20b of the accumulator control valve so that its modulatorpressure is properly modulated to a higher level. The oil pressure thusmodulated is supplied via the oil line f to the brake engaging oilpressure chamber 31 to time the release of said brake B1 properly inaccordance with the control of the aforementioned timing valve 33.

In the 3rd speed state, on the other hand, in which the third clutch C3and the fourth clutch C0 as well as the first clutch C1 are engaged,whereas the first brake B1 is released, the rotation of the input shaft15 is transmitted through the one-way clutch F0 and the third clutch C3to the smaller ring R1 and further through the fourth clutch C0 to thelarger ring gear R2 so that the integral rotation of the planetary gearunit 12 are extracted from the carrier output gear 13.

At this time, the engagement change between the fourth clutch C0 and thefirst brake B1 occurs. However, no shift shock will take place becausethe proper timing is achieved, as described above, and because theshifts via other gear stages are blocked. Simultaneously with this,moreover, the third clutch C3 is also engaged, and this engagementtiming may be slow because said clutch C3 is in parallel with the secondone-way clutch F0.

Next, in the 4th speed state, the first solenoid valve S_(L) 1 is OFF,and the second solenoid valve S_(L) is switched OFF. In this state, the2-3 shift valve 37 is held in its upper half position, and the 3-4 shiftvalve 39 is switched to its upper half position by having its controlchamber 39f fed with the control oil pressure. On the other hand, the1-2 shift valve 36 has its control oil chamber 36d fed with the controloil pressure but its constraining control oil chamber 36g is fed withthe line pressure of the line pressure supply port 37f of the 2-3 shiftvalve 37 via the port 37h, so that the 1-2 shift valve 36 is held in itslower half position. As a result, the 3-4 shift valve 39 has its B₁relief port 39b communicating with the drain port 39e so that the brakeengaging oil pressure chamber 31 of the first brake hydraulic servo B₁is drained.

At the aforementioned 3rd speed, since the oil pressure is supplied tothe fourth clutch hydraulic servo C₀, the oil pressure is supplied viathe oil line c to the control oil chamber 32c of the B₁ modulatorcontrol valve 32 so that this valve 32 is switched to its lower halfposition in which the second input port 32a and the output port 32b arecommunicating with each other. If, in this state, the 3-4 shift valve 39is switched at the 4th speed to have its line pressure supply port 39dcommunicating with the port 39c, the line pressure is fed via the ports39d and 39c and the ports 32a and 32b of the B₁ modulator control valveto the constraining control oil chamber 30c of the B₁ modulator valve 30so that this modulator valve 30 is switched to the line pressure supplystate in which the line pressure port 30b and the pressure modulationport 30a are communicating with each other.

As a result, the line pressure coming from the line pressure isintroduced as is to the oil line f via the ports 30b and 30a so that theoil pressure supplied to the brake engaging oil pressure chamber 31 ofthe first brake hydraulic servo B₁ is switched from the modulatorpressure to the line pressure. At this time, like before, the shift canbe smoothed by controlling the oil pressure to be supplied to the backpressure chamber 7₄ of the accumulator 2₄ on the basis of the electriccontrol of the throttle pressure control valve 5. Despite this fact,however, the engagement of the first brake B1 is controlled by adjustingthe drain oil pressure from the brake releasing oil pressure chamber 35by means of orifices 83a, 83b, 83c and so on.

Since the 3-4 shift valve 39 has its C3 timing port 39i communicatingwith the drain port 39j, the oil pressure of the third hydraulic servoC₃ is drained through a check valve 85 and the C3 timing valve 80 andvia the ports 39i and 39j of the 3-4 shift valve 39.

Incidentally, in the 4th speed state, the throttle pressure controlvalve 5 is controlled to a rather high level by the electric signalcoming from the control unit, and the accumulator back pressure or theoutput pressure of the accumulator control valve 20 is also set to arather high level.

In the 4th speed state, the first clutch C1 and the fourth clutch C0 arein their engaged states, and the first brake B1 is switched to itsengaged state whereas the third clutch C3 is switched to its releasedstate. In this 4th speed state, the rotation of the input shaft 15 istransmitted through the fourth clutch C0 to the larger ring gear R2. Atthe same time, the sun gear S is stopped by the first brake B1 so thatthe rotation of said larger ring gear R2 rotates the carrier CR at ahigh speed while rotating the ring gear R1 idly. The rotation of thecarrier CR is transmitted to the output gear 13.

At this time, the first brake B1 is engaged, and the third clutch C3 isreleased. Even if, however, the third clutch C3 is prematurely released,the 3rd speed state is maintained by the second one-way clutch F0. As aresult, the shift shocks, which might otherwise be caused by theengagement change, can be prevented by delaying the engagement of thefirst brake B1 by means of the orifices 83a to 83c.

At downshift from the 4th to 3rd speeds, on the other hand, the 3-4shift valve 39 is switched to its lower half position, as has beendescribed hereinbefore, the oil pressure of the oil line b is suppliedvia the ports 39a and 39b to the brake releasing oil pressure chamber 35of the first brake hydraulic servo B₁, and the line pressure of the linepressure supply port 39d is supplied via the port 39i and thorough theC3 timing valve 80 and the C₃ modulator valve 68 to the third clutchhydraulic servo C₃.

At this time, the release oil pressure to be supplied to the brakereleasing oil pressure chamber 35 of the hydraulic servo B₁ iscontrolled by means of the orifices 83b and 83c, and the second one-wayclutch F0 is switched from overrun to engagement, so that the shift canbe smoothly effected.

At the downshift from the 3rd to 2nd speed, moreover, the 2-3 shiftvalve 37 is switched to its lower half position, as has been describedhereinbefore, to have its C₀ port 37b and drain port 37c communicatingwith each other. Then, the oil pressure in the brake releasing oilpressure chamber 35 of the hydraulic servo B₁ is drained at first fromthe drain port 37c via the ports 39b and 39a, the oil line d, the oilline e, the oil line b and the port 37b, and the oil pressure of thethird clutch hydraulic servo C₀ is drained together with the oilpressure of the accumulator chamber 9₃ of the accumulator 2₃ from thedrain port 37c via the oil line b and the port 37b.

As a result, the release of the fourth clutch C0 is delayed relative tothe engagement of the first brake B1 thereby to prevent the shiftingoperations from the 3rd through 1st to 2nd speeds, namely, the shiftwhich will pass the 1st speed state with both the fourth clutch C0 andthe first brake B1 released. Incidentally, at the downshift from the 3rdto 2nd speeds, the C3 timing valve 80 is switched to its lefthand halfposition by having its constraining control oil chamber 80b relievedfrom the oil pressure based upon the hydraulic servo C₀, so that the oilpressure of the hydraulic servo C₃ is drained via the check value 85from the drain port of the C3 timings valve 80. At the downshift fromthe 2nd to 1st speeds, moreover, the 1-2 shift valve 36 is switched toits upper half position to have its output port 36b communicating withits drain port 36c. As a result, the oil pressure of the brake engagingoil pressure chamber 31 of the first brake hydraulic servo B₁ isdischarged to the drain port 36c from the oil line f, the ports 30a and30b of the B₁ modulator valve 30, the check value 99, the oil line a andthe port 36b.

At the kickdown from the 4th to 2nd speeds, on the other hand, the 3-4shift valve 39 is switched to its lower half position, and the 2-3 shiftvalve 37 is also switched to its lower half position. As a result, theoil pressure of the fourth clutch hydraulic servo C₀ is discharged fromthe drain port 37c via the oil line b and the port 37b, and the oilpressure of the brake releasing oil pressure chamber 35 of the firstbrake hydraulic servo B₁ is also discharged from the drain port 37c viathe ports 39a and 39b, the oil line d, the check value 41, the oil linese and a and the port 37b.

At this time, the B₁ modulator control valve 32 is switched to itsrighthand half position by having its control oil chamber 32c relievedfrom its oil pressure based upon the hydraulic servo C₀. At the sametime, the B₁ modulator control valve 32 has its input port 32a drainedto relieve the constraining pressure of the constraining control oilchamber 30c of the B₁ modulator valve 30 so that this valve 30 generatesthe modulator valve pressure. However, the B₁ modulator valve 30 is heldin its line pressure supplied state because the line pressure isinstantly supplied to the port 32d of the control valve 32 via the port37i of the 2-3 shift valve 37 and further to the constraining controloil chamber 30c via the port 32b.

As a result, the first brake B1 is maintained in its engaged statewithout passing through any release so that the downshift is quickly andsmoothly effected by the single operation. If, on the other hand, themanual valve 62 is shifted to the R range, the line pressure is suppliedfrom the R range port to the second clutch hydraulic servo C₂ and itsaccumulator 2₂. At this time, like before, the throttle pressure controlvalve 5 is properly controlled to the proper level by the electricsignal coming from the control unit, and the oil pressure having actedupon the accumulator control valve 20 and dropped from the line pressureis supplied to the back pressure chambers 7₁ to 7₄ of the accumulators2₁ to 2₄ to control the back pressure of the accumulator 2₂. As aresult, the oil pressure of the hydraulic servo C₂ is controlled tocorrespond to the engagement characteristics of the second clutch C2 sothat the shifts from the N to R ranges or from the D to R ranges can besmoothed. In this reverse (R) range, that is, in case the vehicle isrunning at a predetermined low speed, e.g., 7 Km/H or substantially inthe halted state, the 1-2 shift valve 36 is in its upper half position,and the line pressure from the R range port is supplied to the secondbrake hydraulic servo B₂ through the two-way check valve and via theports 36f and 36e. In the reverse state, moreover, in which the secondclutch C2 and the second brake B2 are engaged, the rotation of the inputshaft 15 is transmitted through the second clutch C2 to the sun gear S.Since, moreover, the larger ring gear R2 is stopped by the second brakeB2, the rotation of said sun gear S is reversed and transmitted to thecarrier CR, while reversing the smaller ring gear R1 idly, so that thesereverse rotations are extracted from the output gear 13.

In the reverse range, moreover, in case the vehicle is coasting at apredetermined speed or more, the second solenoid valve S_(L) 2 is turnedON to switch the 1-2 shift valve 36 to its lower half position. Instate, no oil pressure is supplied to the second brake hydraulic servoB₂ so that the aforementioned reverse state is not effected.

If the manual valve 62 is shifted to the 2nd range, on the other hand,the line pressure of the 2nd range port is supplied to the constrainingcontrol oil chamber 39h of the 3-4 shift valve 39 so that this valve 39is blocked from coming into its upper half position, i.e., the 4th speedposition.

Moreover, the line pressure of the 2nd range port is supplied to theconstraining control oil chamber 80b of the C3 timing valve 80 to holdthis valve 80 in its righthand half position so that the third clutchhydraulic servo C₃ is always supplied with the oil pressure at the 1st,2nd and 3rd speeds.

As a result, the input shaft 15 and the smaller ring gear R1 areconnected through the third clutch C3 so that braking by the engine isachieved by eliminating the coasting of the vehicle, which mightotherwise be caused by the overrun of the second one-way clutch FO.

If, moveover, the manual valve 62 is shifted to the 1st range, the linepressure of the 1st range port is supplied to the constraining controloil chamber 37e of the 2-3 shift valve 37 so that this valve 37 isblocked from coming into its upper half position, i.e., the 3rd and 4thspeed positions. The line pressure of the 1st range port is reduced by alow pressure modulator valve 79. This modulated pressure is suppliedthrough the two-way check valve to the port 36f of the 1-2 shift valve36 and further to the second brake hydraulic servo B₂ at the 1st speed.Incidentally, the embodiment thus far described uses the B₁ modulatorcontrol valve 32, which is not always indispensable.

As shown in FIG. 1, drum 111 of the clutch C1 has its rotatablysupporting portion 112 splined on its inner face to the input shaft 15.Moreover, a piston member 113 is fitted in the drum 111 of the clutchC1, and a spring 116 is interposed between the piston member 113, and astop ring 115 at the back of the piston member 113, thus forming thehydraulic servo for the clutch C1. On the other hand, the clutch C1 isinterposed between the inner circumference of the outer flange portionof the drum 111 of the clutch C1 and a hub portion 119 which isprojected toward the C1 drum 111 from the radial flange portion of aclutch CO drum 117. The rotatably supporting portion 120 of the clutchCO drum 117 is supported for relative rotation on the outercircumference of the rotatably supporting portion 112 of the drum 111 ofthe clutch C1 by a bearing 121.

In the drum 117 of the clutch CO, there are fitted two piston members,the larger one 122 of which receives a smaller one 123 in its recess.The larger piston 122 constitutes the hydraulic servo for engaging orreleasing the clutch CO, whereas the smaller piston 123 constitutes thehydraulic servo for engaging or releasing the clutch C3. In other words,the clutches C3 and CO are interposed between the inner circumference ofthe outer side of the clutch CO drum 117 and the ring gears R1 and R2 ofthe single planetary gear 10 and the dual planetary gear 11. On theother hand, the clutch C1 is connected to the ring gear R1 of the singleplanetary gear 10 through the CO drum 117 and the one-way clutch FO.

The oil pressure for actuating the clutches C0 and C3 is suppliedthrough section 125 of a transmission casing 17a. This section 125 hasits oil passage 126 extended through the inner face of the rotatablysupporting portion 112 of the clutch C1 drum 111 and further through anoil passage 127 formed in the outer surface of said rotatably supportingportion 112. Oil pressure is applied to the backs of the larger piston122 and the smaller piston 123 through an oil passage 128 formed in theouter surface of the rotatably supporting portion 120 of the C0 drum117.

Thus, the inner circumference of the drum rotatably supporting portionof the clutch C0 acting as the O/D mechanism is arranged over the innercircumference of the drum rotatably supporting portion 112 of the clutchC1 so that the axial size of the clutch C0 drum 117 can be reduced.Since, moreover, the clutch C0 can be engage with the ring gear R2 ofthe dual planetary gear 11 within the radial dimension of the clutch C1,the radial size can also be reduced.

Since, furthermore, the clutch C1 drum 111 is adjacent to thetransmission casings 17a, the C1 clutch drum 111 rotating at all timescan be easily used as the output to the input shaft r.p.m. sensor.

We claim:
 1. An automatic transmission comprising:a planetary gear unithaving a plurality of rotary components and a reaction member; an inputshaft connected to at least a first of said rotary components; an outputshaft connected to a second of said rotary components; a brake forselectively braking said reaction member; a first clutch systemcomprising: a first drum; a first hub member fixed to said first drumslidably mounted on and rotating with said input shaft; a first clutchmounted within said first drum; a first piston slidably mounted in saidfirst drum for selectively engaging said first clutch; and a secondclutch system comprising:a second drum; a second hub member fixed tosaid second drum and rotatably mounted on said first hub member; aradially extending portion connecting said second drum with said secondhub; an axial extension fixed to said radially extending portion, saidfirst clutch selectively connecting said axial extension with said firstdrum; a second clutch for selectively connecting said second drum withone of said rotary components; and a second piston slidably mounted insaid second drum for selectively engaging said second clutch.
 2. Anautomatic transmission in accordance with claim 1 wherein saidtransmission includes a casing having an axial extension receiving oneend of said input shaft, said axial extension rotatably supporting aportion of said first hub member with a second portion of said hubmember being splined to said input shaft.
 3. An automatic transmissionin accordance with claim 1 wherein said automatic transmission has acasing including an axially extending portion and a radially extendingportion covering one end of said axially extending portion, said firstdrum being located axially between said radially extending portion ofsaid casing and said second drum.